1. Field of the Invention
This invention relates, generally, to motor control switches and, more specifically, to a limit switch mechanism for controlling the electric motor which powers an electric garage door opening and closing mechanism. There are many different types of so-called limit switches used in regulating and controlling the motor of a garage door opener. There are various safety requirements as well as installation problems associated with the varying structure and circumstances encountered at the site at which the garage door opener is to be installed.
Apart from the safety switches, which are necessary to control movement of the door when an object is encountered, it is also necessary to have controls which limit the movement of the garage door from between the fully raised and the fully closed positions. Because of the variations in door structures and the circumstances relating to the installation of the opener mechanism with its associated connections to the garage door, it is necessary that means be included in the limit switch mechanism to permit adjustment of the switching points so that they will be synchronized with the opened or closed position of the door.
In general the garage door switches have been complicated and difficult to install. The present invention involves a simple mechanism driven by the electric motor for the opener which has means for easily and simply adjusting the desired switch operating positions while leaving the limit switches themselves fixedly mounted with respect to their supporting frame.
2. Description of the Prior Art
The prior art includes a number of patents which disclose the broad idea of utilizing a motor driven threaded shaft with an axially translatable actuator to control other operations. Among this prior art is Fry U.S. Pat. No. 3,209,090, Hummel U.S. Pat. No. 1,788,302, and Hubers U.S. Pat. No. 1,457,367. The mechanisms disclosed in the above cited patents are relatively complex. The patent to Hubers discloses a split switch actuator which travels axially along a motor driven shaft and which may be repositioned by disengaging the switch actuator from the threaded shaft. Other prior art patents showing similar actuators travelling on motor driven shafts are Gibson et at. U.S. Pat. No. 2,504,018, Layer U.S. Pat. No. 4,838,403, and Layer et al. U.S. Pat. No. 4,721,196. These last cited patents disclose complex mechanisms for operating mechanical devices in general rather than switching applications of the kind herein involved.